The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A substrate processing system may be used to etch film on a substrate such as a semiconductor wafer. The substrate processing system typically includes a processing chamber, a gas distribution device and a substrate support. During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the processing chamber and radio frequency (RF) plasma may be used to activate chemical reactions.
The substrate processing chamber may include a measurement device (e.g., a spectral reflectometer, such as a laser spectral reflectometer, or LSR, or another light measurement device) positioned to measure various characteristics of a substrate arranged on the substrate support. For example, the measurement device may be positioned directly above the substrate support to direct a signal downward at the substrate. A sensing device (e.g., a charge-coupled device, or CCD, a photodiode, etc.) is arranged to sense the signal reflected from the surface of the substrate. Characteristics of the reflected signal are indicative of various characteristics of the substrate.